Seal for pem fuel cell plate

ABSTRACT

A seal structure is disclosed for forming a substantially fluid tight seal between a UEA and a plate of a fuel cell system, the seal structure including a sealing member formed in one fuel cell plate, a seal support adapted to span feed area channels in an adjacent fuel cell plate, and a seal adapted to cooperate with a UEA disposed between the fuel cell plates, the sealing member, and the seal support to form a substantially fluid tight seal between the UEA and the one fuel cell plate. The seal structure militates against a leakage of fluids from the fuel cell system, facilitates the maintenance of a velocity of a reactant flow in the fuel cell system, and a cost thereof is minimized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/479,444 filed on May 24, 2012, which is a divisional of U.S. patentapplication Ser. No. 12/099,393, filed on Apr. 8, 2008. The entiredisclosures of the above applications are incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to a fuel cell system and more particularly to aseal for sealing between plates of the fuel cell system.

BACKGROUND OF THE INVENTION

Fuel cell systems are increasingly being used as a power source in awide variety of applications. Fuel cell systems have been proposed foruse in power consumers such as vehicles as a replacement for internalcombustion engines, for example. Such a system is disclosed in commonlyowned U.S. patent application Ser. No. 10/418,536, hereby incorporatedherein by reference in its entirety. Fuel cells may also be used asstationary electric power plants in buildings and residences, asportable power in video cameras, computers, and the like. Typically, thefuel cells generate electricity used to charge batteries or to providepower for an electric motor.

Fuel cells are electrochemical devices which combine a fuel such ashydrogen and an oxidant such as oxygen to produce electricity. Theoxygen is typically supplied by an air stream. The hydrogen and oxygencombine to result in the formation of water. Other fuels can be usedsuch as natural gas, methanol, gasoline, and coal-derived syntheticfuels, for example.

The basic process employed by a fuel cell is efficient, substantiallypollution-free, quiet, free from moving parts (other than an aircompressor, cooling fans, pumps and actuators), and may be constructedto leave only heat and water as by-products. The term “fuel cell” istypically used to refer to either a single cell or a plurality of cellsdepending upon the context in which it is used. The plurality of cellsis typically bundled together and arranged to form a stack with theplurality of cells commonly arranged in electrical series. Since singlefuel cells can be assembled into stacks of varying sizes, systems can bedesigned to produce a desired energy output level providing flexibilityof design for different applications.

A common type of fuel cell is known as a proton exchange membrane (PEM)fuel cell. The PEM fuel cell includes three basic components: a cathode,an anode and an electrolyte membrane. The cathode and anode typicallyinclude a finely divided catalyst, such as platinum, supported on carbonparticles and mixed with an ionomer. The electrolyte membrane issandwiched between the cathode and the anode to form amembrane-electrode-assembly (MEA). The MEA is disposed between porousdiffusion media (DM). The DM facilitates a delivery of gaseousreactants, typically the hydrogen and the oxygen from air, to an activeregion defined by the MEA for an electrochemical fuel cell reaction.Nonconductive gaskets and seals electrically insulate the variouscomponents of the fuel cell.

When the MEA and the DM are laminated together as a unit, for example,with other components such as gaskets and the like, the assembly istypically referred to as a unitized electrode assembly (UEA). The UEA isdisposed between fuel cell plates, which act as current collectors forthe fuel cell. The UEA components disposed between the fuel cell platesare typically called “softgoods”. The typical fuel cell plate has a feedregion that uniformly distributes the gaseous reactants to and betweenthe fuel cells of the fuel cell stack. The feed region may have a broadspan that facilitates a joining of the fuel cell plates, e.g., bywelding, and a shifting of flows between different elevations within thejointed plates. The feed region includes supply ports that distributethe gaseous reactants from a supply manifold to the active region of thefuel cell via a flow field formed in the fuel cell plate. The feedregion also includes exhaust ports that direct the residual gaseousreactants and products from the flow field to an exhaust manifold.

The stack, which can contain more than one hundred plates, iscompressed, and the elements held together by bolts through corners ofthe stack and anchored to frames at the ends of the stack. In order tomilitate against undesirable leakage of fluids from between the plateassemblies, a seal is often used. The seal is disposed along aperipheral edge of the plate assemblies and selected areas of the flowpaths formed in the plates. Prior art seals have included the use ofmetal seals, elastomeric seals, and a combination thereof. The prior artseals have performed adequately for prototyping. However, a cost of theprior art seals and a sensitivity of the prior art seals to dimensionaland environmental variation makes a use thereof undesirable for fullscale production

The prior art seals typically require the fluids to follow a tortuousflow path through the fuel cell. The tortuous flow path typicallyincludes open areas which reduce a velocity of the flow of the fluids.The reduced velocity of the fluids can adversely affect the performanceof the fuel cell stack. Additionally, the reduced velocity of the fluidshas been known to contribute to an accumulation of water in the flowpaths, which can block the flow of the fluids within at least a portionof the fuel cell stack and reduce the electrical output thereof.

It would be desirable to produce a seal assembly for sealing betweenplates of a fuel cell system, wherein the seal assembly militatesagainst a leakage of fluids from the fuel cell system, facilitates amaintenance of a desired velocity of the fluid flow in the fuel cellsystem, and a cost thereof is minimized.

SUMMARY OF THE INVENTION

Compatible and attuned with the present invention, a seal assembly forsealing between plates of a fuel cell system, wherein the seal assemblystructure militates against a leakage of fluids from the fuel cellsystem, facilitates a maintenance of a desired velocity of the reactantflow in the fuel cell system, and a cost thereof is minimized, hassurprisingly been discovered.

In one embodiment, a plate for a fuel cell comprises a plate with afirst surface, a second surface, and a plurality of header openingsformed therein; a flow field formed on the first surface of the plate,the flow field including an inlet feed region and an outlet region, theinlet region and the outlet region having feed area channels to providefluid communication with at least one header opening; and at least oneelongated sealing member formed on the plate adapted to cooperate with aseal assembly to form a substantially fluid tight seal therebetween.

In another embodiment, a seal assembly for a fuel cell comprises a fuelcell plate with a first surface, a second surface, and a plurality ofheader openings formed therein; a flow field formed on the first surfaceof the plate, the flow field including an inlet feed region and anoutlet region, the inlet region and the outlet region having feed areachannels to provide fluid communication with at least one headeropening; at least one elongate sealing member formed on the plateincluding a first lateral side and a spaced apart second lateral sidewith at least one sealing surface disposed therebetween; and at leastone sealing component adapted to cooperate with the sealing member toform a substantially fluid tight seal therebetween.

In another embodiment, a fuel cell stack comprises at least one endplate having a flow field formed on a surface thereof and a plurality ofheader openings formed therein in selected fluid communication with theflow field, the flow field including an inlet feed region, an outletregion, a plurality of feed area channels in selected fluidcommunication with the inlet region and the outlet region, and at leastone sealing member formed around at least one of the header openingsformed in the end plate; at least one bipolar plate disposed adjacentthe end plate, wherein each bipolar plate includes, a flow field formedon at least one of a first surface and a second surface and a pluralityof header openings formed therein in selected fluid communication withthe flow field, the flow field including, an inlet feed region, anoutlet region, a plurality of feed area channels in selected fluidcommunication with the inlet region and the outlet region, and at leastone sealing member formed around at least one of the header openingsformed in the bipolar plate; a unitized electrode assembly disposedbetween each plate; and a seal having a first surface and a secondsurface, the first surface adapted to form a substantially fluid tightseal with the sealing member of at least one of the end plate and thebipolar plate; and a seal support having a first surface and a secondsurface, the first surface adapted to form a substantially fluid tightseal with one of the second surface of the seal and the unitizedelectrode assembly.

DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description of a preferred embodiment when considered in thelight of the accompanying drawings in which:

FIG. 1 is an exploded perspective view of a proton exchange membranefuel cell stack according to an embodiment of the invention;

FIG. 2 is a fragmentary perspective view of a fuel cell plate of thefuel cell stack shown in FIG. 1;

FIG. 3 a is a fragmentary cross sectional view of a sealing memberformed in the fuel cell plates shown in FIG. 1 and FIG. 2 taken alongline 3-3 in FIG. 2;

FIG. 3 b is a fragmentary cross sectional view of a sealing memberaccording to another embodiment of the invention;

FIG. 3 c is a fragmentary cross sectional view of a sealing memberaccording to another embodiment of the invention;

FIG. 3 d is a fragmentary cross sectional view of a sealing memberaccording to another embodiment of the invention;

FIG. 4 a is a fragmentary perspective view of a seal assembly betweentwo adjacent fuel cell plates at a reactant header taken along line 4-4in FIG. 1;

FIG. 4 b is a fragmentary perspective view of a seal assembly accordingto another embodiment of the invention;

FIG. 5 is a fragmentary perspective view of the seal assembly at areactant header in a terminal side of an end plate taken along line 5-5in FIG. 1; and

FIG. 6 is a fragmentary perspective view of a seal formed between twoadjacent fuel cell plates at a coolant header taken along line 6-6 inFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description and appended drawings describe andillustrate various exemplary embodiments of the invention. Thedescription and drawings serve to enable one skilled in the art to makeand use the invention, and are not intended to limit the scope of theinvention in any manner.

FIG. 1 is schematic illustration of a proton exchange membrane (PEM)fuel cell stack 10 having two electricity producing cells 12 and 14.Although a bipolar PEM fuel cell stack is shown, it is understood thatother fuel cell types and configurations can be used without departingfrom the scope and spirit of the invention. It is also understood thatfuel cell stacks having more cells and plates can be and typically areused.

The fuel cell stack 10 includes a first a unitized electrode assembly(UEA) 16 and a second a UEA 18. The UEA's 16, 18 include amembrane-electrode-assembly (MEA) (not shown) disposed between porousdiffusion media (DM) (not shown). It should be understood that the MEAand the DM can be separate components rather than being combined to formthe UEA. The UEA's 16, 18 are disposed between fuel cell plates, whichact as current collectors for the fuel cell. An electrically conductive,liquid-cooled, bipolar plate assembly 20 is disposed between the firstUEA 16 and the second UEA 18. The first UEA 16, the second UEA 18, andthe bipolar plate assembly 20 are stacked together between monopolar endplate assemblies 22, 24. In the illustrated embodiment, the monopolarend plate assemblies 22, 24 are bipolar plate assemblies adapted tofunction as monopolar end plate assemblies. Electrically conductiveadapter plates 25, 25′ are provided to cooperate with a bipolar platethat is identical to bipolar plate 20 to form each of the monopolar endplate assemblies 22, 24. It should be understood that end platesspecifically adapted to function as end plates may also be employed.

The bipolar plate assembly 20 is formed from a pair of plates 26, 26′,more clearly illustrated in FIG. 2. Each plate has a first surface 28,28′, a second surface 30, 30′ and an outer peripheral edge 32, 32′. Thesecond surfaces 30, 30′ of the plates 26, 26′ are bonded together invertical alignment to form a coolant chamber 34 therebetween. The plates26, 26′ can be bonded by various means such as welding or an applicationof an adhesive, for example. The plates 26, 26′ are typically formedfrom a planar metal sheet by a stamping operation, although othermethods can be used as desired.

Each plate 26, 26′ includes a flow field 36 formed on the first surface28, 28′ respectively. FIG. 2 shows the flow field 36 formed in the plate26. It should be understood that the plate 26′ includes a flow field onthe first surface 28′ having the same structural aspects as the flowfield 36 formed on the first surface 28 of the plate 26. However, forclarity, FIG. 2 does not include references to the flow field formed inplate 26′. The flow field 36 distributes a fuel and an oxidant gas tothe cells 12, 14 over the respective faces of the UEA's 16, 18. Theplate 26, 26′ includes header openings 40, 40′ formed therein to providean inlet for the hydrogen and the oxygen to the cells 12, 14. Feed areachannels 50 are formed in the inlet region 38 to provide fluidcommunication between the header opening 40 and the flow field 36.Additionally, header opening 42 is formed in the plate 26, 26′ toprovide an inlet for the coolant to the chamber 34. The plate 26, 26′includes header openings 46, 46′ formed therein to provide an outlet forthe hydrogen and the oxygen from the cells 12, 14. Feed area channels 52are formed in the outlet region 44 to provide fluid communicationbetween the header opening 46 and the flow field 36. Additionally,header opening 48 is formed in the plate 26, 26′ to provide an outletfor the coolant from the chamber 34.

Flow channels (not shown) may be formed in plates 26, 26′ to providefluid communication with the coolant chamber 34 and the respectiveheader openings 42, 48. Alternatively, apertures (not shown) may beformed in the plates 26, 26′ adjacent header openings 42, 48 to providefluid communication with the coolant chamber 34 and the respectiveheader opening 42, 48. It should be understood that both the flowchannels and the apertures may be formed in the plates 26, 26′ toprovide fluid communication with the coolant chamber 34 and therespective header opening 42, 48.

Sealing members 100, more clearly illustrated in FIGS. 3 a to 3 d anddescribed herein below, are formed as an elongate protuberance in theplates 26, 26′ adjacent to and circumscribing the header openings 40′,46′ to form a substantially fluid tight seal therearound. The sealingmember 100 is also formed around the aperture 42 to form a substantiallyfluid tight seal therearound and militate against a coolant from flowingbetween adjacent fuel cell plates 20, 22, 24. It should be understoodthat the sealing members can be formed adjacent to and circumscribingthe header openings 40, 46, 48 rather than header openings 40′, 46′, 42,or elsewhere on the plates 26, 26′ as desired.

As illustrated in FIG. 1, the end plates 22, 24 and the bipolar plate 20are in substantial vertical alignment, placing the respective headeropenings 40, 40, 42, 46, 46′, 48 therein in alignment to form a fuelsupply header and a fuel exhaust header, an oxidant supply header and anoxidant exhaust header, and a coolant supply header and a coolantexhaust header. In the embodiment described herein, the fuel ishydrogen, the oxidant is oxygen, and the coolant is water, although itshould be understood that other fuels, oxidants, and coolants can beused as desired.

The fuel cell stack 10 typically includes clamping plates (not shown) ateach end of the fuel cell stack 10. The clamping plates are adapted toprovide a compressive force on the fuel cell stack 10. The clampingplates include a plurality of inlets and outlets, the inlets and outletsproviding fluid communication between the fuel cell 10 and a source ofreactants and coolant, and an exhaust of the reactants and coolants,respectively.

A seal assembly 200, more clearly illustrated in FIGS. 4 a and 4 b anddescribed herein below, is provided between adjacent header openings 40,40′, 46, 46′ in each of the respective plates 22, 20 and 20, 24. Theseal assembly 200 is adapted to cooperate with the sealing member 100and the adjacent UEA 16, 18 to form a substantially fluid tight sealbetween the sealing member 100 and the adjacent UEA 16, 18. In theembodiment shown in FIG. 1, the seal assembly 200 forms a continuousring circumscribing an area to be sealed. It should be understood thatthe seal assembly 200 can be adapted to seal a single edge or anyportion of an edge.

A modified seal assembly 300, more clearly illustrated in FIG. 5 anddescribed herein below, is provided between selected apertures formed inthe electrically conductive plates 25, 25′ and the header openings 40,40′, 46, 46′ in the respective end plates 22, 24. The modified sealassembly 300 is adapted to cooperate with the electrically conductiveplates 25, 25′ and the adjacent end plates 22, 24 to block the flow ofreactants across the flow field 36 adjacent the conductive plate. Byblocking the reactant flow across the flow field 36 in one of the plates26, 26′ forming the end plates 22, 24, the end plates 22, 24 canfunction as monopolar plates.

FIG. 3 a illustrates a cross section of the sealing member 100 formed inthe plate 26 according to one embodiment of the invention. The sealingmember 100 has a first lateral side 102 and a spaced apart secondlateral side 104, each having an upper end 106, 106′, respectively. Asubstantially planar sealing surface 108 is disposed between therespective upper ends 106, 106′. The planar sealing surface 108 isrecessed in respect of the upper ends 106, 106′. Recessing the planarsealing surface 108 shields the planar sealing surface 108 from damagesuch as scratches or dents, for example, which could prevent asubstantially fluid tight seal from being formed on the planar sealingsurface 108.

The lateral sides 102, 104 include at least a first radius 110, 110′ anda second radius 112, 112′ respectively. The radii 100, 110′, 112, 112′are adapted to provide a resilient response in the sealing member 100 toa normal load applied to the sealing surface 108. The resiliency of thesealing member 100 facilitates the forming and maintaining of the sealon the sealing surface 108. A dimension of the radii 100, 110′, 112,112′ can be selected to achieve the desired resiliency in the sealingmember 100. Favorable results have been found using radii 100, 110′,112, 112′ between about 0.1 millimeters to 0.5 millimeters, althoughother radii can be used.

FIGS. 3 b and 3 c illustrate a cross section of the sealing member 100′,100″ according to another embodiment of the invention. In FIGS. 3 b and3 c, each of the sealing members 100′ and 100″ has a first lateral side120 and a spaced apart second lateral side 122. A series of fourinterconnected substantially planar segments 124 are formed between thelateral sides 120, 122. The lateral sides 120, 122 and segments 124 areconnected at angles to form three apexes 126 and two troughs 128, eachapex 126 providing a sealing surface. It should be understood that feweror additional segments 124 can be provided to form fewer or additionalapexes 126 and troughs 128 as desired. A radius 130 is typically formedat each apex 126 and trough 128. Favorable results have been found usingradii 130 between about 0.1 millimeters to 0.5 millimeters, althoughother radii can be used.

In FIG. 3 b the sealing member 100′ is formed to locate the troughs 128in an elevated position in respect of the second surface 30 of the plate26. The elevated position of the troughs 128 provide a resilientresponse in the sealing member 100′ to a normal load applied to theapexes 126. Alternatively, as shown in FIG. 3 c, the troughs 128 can belocated substantially coplanar in respect of the second surface 30 ofthe plate 26. The coplanar position of the troughs 128 increases therigidity of the seal member 100″ illustrated in FIG. 3 c as compared tothe seal member 100′ illustrated in FIG. 3 b.

FIG. 3 d illustrates a cross section of the sealing member 100′″according to yet another embodiment of the invention. In FIGS. 3 d, thesealing member 100′″ includes three coextensive elongate protuberances140, 140′, 140″. Each protuberance 140, 140′, 140″ has a first lateralside 142 and a spaced apart second lateral side 144 with a sealingsurface 146 disposed therebetween. It should be understood that fewer oradditional protuberances can be provided as desired. The lateral sides142, 144 include at least a first radius 148, 148′ and a second radius150, 150′ respectively. Favorable results have been found using theradii 148, 148′, 150, 150′ between about 0.1 millimeters to 0.5millimeters, although other radii can be used.

A stretch bending process may be employed to form the sealing member100, 100′, 100″, 100′″ illustrated in FIGS. 3 a to 3 d. The stretchbending process facilitates the removal of surface imperfections in thesealing surfaces 108, 126, 146, and facilitates the modification of aheight of the sealing member 100, 100′, 100″, 100′″ with minimizedstamping tooling changes. It should be understood other processes may beemployed to form the sealing member 100, 100′, 100″, 100″.

FIG. 4 a illustrates the seal assembly 200 according to an embodiment ofthe present invention. The seal assembly 200 includes a substantiallyrigid seal support 202 having a first side 204 and a second side 206.The second side 206 of the seal support 202 is in contact with andadapted to span the feed area channels 50 in the inlet region 38 of theflow field 36 in the fuel cell plate 26′. It should be understood thatthe seal support 202 can be attached to the plate 26′ by welding, forexample or bonded to the UEA with an adhesive. The first side 204 of theseal support 202 is in contact with one side of the UEA 16.

The seal assembly 200 also includes a seal 208 having a first sealingsurface 210 and a second sealing surface 212. The seal 208 is disposedon an opposite surface of the UEA 16 from the seal support 202. Thesecond surface 212 of the seal 208 is in contact with the UEA 16 to forma substantially fluid tight seal therebetween. The first sealing surface210 is in contact with the sealing surface 108 of the sealing member 100formed in the adjacent plate 26, and adapted to form a substantiallyfluid tight seal tight seal between the seal 208 and the sealing surface108.

A printing means may be employed to dispose an elastomeric material onthe UEA 16 to form the seal 208. Additionally, the elastomeric materialmay be dispensed from a nozzle onto the UEA 16 employing a cure in placeprocess. Other methods of application of the seal 208 can be used asdesired. It should be understood that the seal 208 may be disposed onthe sealing member 100. Additionally, it should be understood that theseal 208 can be disposed on a substrate forming a separate component, orcan be a separate component that is placed in a position between thesealing member 100 and the UEA 16.

In the embodiment shown in FIG. 4 a, seal 208 is a single seal, however,it should be understood that the seal 208 can include two or more spacedapart coextensive seals.

In the embodiment illustrated in FIG. 4 a, the seal assembly is showntogether with the sealing member 100 as illustrated in FIG. 3 a. Itshould be understood that the sealing member 100′, 100″, 100′″ asillustrated in FIGS. 3 b to 3 d, respectively, can be employed with theseal assembly 200 shown in FIG. 4 a.

FIG. 4 b illustrates the seal assembly 200 according to anotherembodiment of the present invention. In FIG. 4 b the seal assembly 200′includes the UEA 16 having one side thereof in contact with and spanningthe feed area channels 50 in the inlet region 38, of the flow field 36in the fuel cell plate 26′. A substantially rigid seal support 222having a first side 224 and a second side 226 is disposed adjacent theUEA 16 positioning the second side 226 of the seal support 222 incontact with an opposite side of the UEA 16 from the plate 26′. Itshould be understood that an adhesive can be provided between the secondside 226 of the support 222 and the UEA 16 to facilitate the formationof a substantially fluid tight seal therebetween. The seal support 222supports the UEA 16 in the areas where the UEA 16 spans the respectivefeed area channels 50. A seal 228 having a first sealing surface 230 anda second sealing surface 232 is disposed on the first side 224 of theseal support 222 to position the second sealing surface 232 of the seal228 in contact with the first side 224 of the seal support 222 to form asubstantially fluid tight seal therebetween. The first sealing surface230 of the seal 228 is in contact with the apexes 126 of the adjacentsealing member 100′. The first sealing surface 230 is adapted to form asubstantially fluid tight seal between the seal 228 and the apexes 126formed in the adjacent plate 26.

The elastomeric material may be dispensed from a nozzle onto the sealsupport 222 employing a cure in place process. Other methods ofapplication of the seal 228 can be used as desired. It should beunderstood that the seal 228 may be disposed on the sealing member 100′rather than or in addition to the seal support 222.

In the embodiment shown in FIG. 4 b, seal 228 provides a single sealmember, however, it should be understood that the seal 228 can includetwo or more spaced apart coextensive seals. Additionally, the sealassembly 200′ is shown as it would appear with the seal members 100′ asillustrated in FIG. 3 b. It should be understood that the seal members100′, 100″, 100′ as illustrated in FIGS. 3 a, 3 c, and 3 d,respectively, can be employed with the seal assembly 200′ shown in FIG.4 b.

The seal assemblies 200, 200′ illustrated in FIGS. 4 a and 4 bcompensate for a misalignment between the components of the fuel cellstack 10 which would otherwise result in a reduction in theeffectiveness of the seal assembly 200, 200′. A width of the sealsupport 202, 222 is greater than a width of the sealing surface in thesealing member 100, 100′. The sealing member 100, 100′ can have somedegree of a lateral misalignment in respect of an adjacent fuel cellplate due to a manufacturing variation, for example. Because the sealsupport 202, 222 is wider than the sealing surface in the sealing member100, 100′, the sealing member 100, 100′ does not require exact alignmentwith the adjacent seal assembly 200, 200′ to form a seal therewith. Theseal assembly 200, 200′ can form a seal within a predetermined range ofmisalignment. It is understood the range of misalignment can be adjustedas desired by changing a width of the seal support 202, 222.

In FIGS. 4 a and 4 b, the seal supports 202, 222 are shown assubstantially planar in the assembled fuel cell stack 10. It should beunderstood that the seal supports 202, 222 can be formed to a shape thatimparts a resiliency thereto. For example, the seal support can beformed to have a curved shape in a relaxed condition by having an innerand an outer edge thereof curve concavely toward the adjacent feed areachannels 50. The curved seal support may be deflected to a substantiallyplanar position, as illustrated in FIGS. 4 a and 4 b when the fuel cellstack 10 is assembled and a compressive load applied. By curving theseal supports 202, 222, a resiliency or a spring like response isprovided thereto. The resiliency of the curved seal support facilitatesthe forming and maintaining of the substantially fluid tight seal.Further, the seal supports 202, 222 may include at least one non-planarelement such as an inflection or a ridge, for example, to facilitate theforming and maintaining of the substantially fluid tight seal betweenthe seal supports 202, 222 and the UEA 16 or seal 228, respectively.Favorable results have been obtained using a spring steel for the sealsupports 202, 222, although other materials can be used as desired.

It has been found that the material removed from the plates 26, 26′ toform the header openings 40, 40′, 46, 46′ therein may be employed toform the seal supports 202, 222 for the seal assembly 200. Savings intooling costs, material costs, and process time have also been achievedby forming the seal supports 202, 222 from the material removed from theplates 26, 26′ to form the header openings 40, 40′, 46, 46′ therein.However, other materials can be used.

it should be understood that a thickness or a rigidity can be providedto the UEA 16 or other substrate to eliminate the need for the sealsupports 202, 222 in the seal assembly 200. With such a UEA orsubstrate, the thickness or rigidity of the substrate or UEAsubstantially uniformly transfers the contact force provided by theclamping plates through the fuel cell stack 10 to form the substantiallyfluid tight seal between the seal assemblies 200 and the adjacentsealing members 100.

The seal assembly 200 enables a fluid or a media to flow through thefeed area channels 50, 52 past the seal assembly 200. The fluid, eitherthe fuel or the oxidant in the embodiment shown, enters the flow field36 and exits the flow field 36 by flowing through the respective feedarea channels 50, 52 that are spanned by the seal support 202 or 222.The feed area channels 50, 52 form a straight through tunnel-plate flowpath which militates against a reduction in the velocity of the fluid asit passes therethrough. Additionally, by utilizing the straight throughtunnel-plate flow path, the fluid is not caused to pass through anyportion of the chamber 34 within the bipolar plate 20 or the end plates22, 24, which is typically required when employing a prior art seal. Theelimination of passing the fluid through the chamber 34 maximizes acapacity of the chamber 34 to receive the coolant. It should beunderstood that a width of the feed area channels 50, 52 may be reducedor increased in the area of the seal assembly 200 in respect of thewidth of the channels in other areas of the flow field 36. The width ofthe feed area channels 50, 52 can be selected to optimize the width ofthe spanned feed area channels 50, 52 in respect of the rigidity of theseal supports 202, 222 and to effect the velocity of the reactant flowtherethrough.

The compressive force provided by the clamping plates causes acompression of the fuel cell stack 10, and, consequently, the sealingmembers 100 and the seal assemblies 200 therein. The compression resultsin a contact force between the seals 208, 228 and components adjacentthereto. Additionally, the contact force secures the UEA's 16, 18 withinthe fuel cell stack 10.

An overall height or stack height of the fuel cell 10 will typicallychange during the operation thereof. Such changes can result fromthermal expansions and contractions of the components therein, as wellas a swelling of the UEA's 16, 18 due to a humidification thereof. Whenthe fuel cell is operating at low temperatures, for example, the priorart fuel cell seals often cannot maintain a substantially fluid tightseal between adjacent plates and are prone to leaking. Further, at amaximized stack height, when the fuel cell is operating at an elevatedtemperature and with UEA swell, for example, the prior art seals withlimited elastic response cause the contact force between the UEA's 16,18 and the adjacent plates 20, 22, 24 to decrease, which can cause fluidleaks between adjacent plates. The increased resiliency provided by thesealing member 100 and the sealing member seal assembly 200 militatesagainst leaks between adjacent fuel cell plates 20, 22, 24 duringtypical operating conditions or operation at elevated temperatures, lowtemperatures, and UEA swell.

The resilient nature of the combined sealing member 100 and the sealassembly 200 of the present invention also optimizes the disassembly andrebuilding process of the fuel cell stack 10. For example, the fuel cellplates 20, 22, 24 utilizing the sealing member 100 can be reused sincedeformation of the sealing member 100 is minimized. The fuel cell stack10 can be disassembled; components of the fuel cell stack 10, such asthe UEA 16, 18 and the sealing assembly 200 can be replaced; and thefuel cell 10 can then be reassembled with the original fuel cell plates20, 22, 24. The resilient nature of the combined sealing member 100 andthe seal assembly 200 allows the seal between adjacent plates to bereestablished while substantially maintaining the original height of thefuel cell stack 10.

As previously indicated, a bipolar plate, such as bipolar plate 20, canbe modified to form the monopolar end plates 22, 24 for the fuel cellstack 10. The formation of the end plates 22, 24 from a bipolar plateeliminates the need to produce a separate end plate which would requireadditional tooling and manufacturing costs to produce. The modified sealassembly 300 illustrated in FIG. 5 is adapted to cooperate with abipolar plate 302 and the conductive plate 25′ to form an end plate suchas the end plates 22, 24 shown in FIG. 1. The plate 302 has a first side304 and a second or terminal side 306. The first side 304 forms an anodeplate or a cathode plate for a respective end of the fuel cell stack 10.The terminal side 306 of the end plate 302 does not receive a flow offuel or oxidant and therefore feed area channels 308 must be blocked offfrom header opening 310 to prevent the flow of reactants across theterminal side 306 of the end plate 302.

The modified seal assembly 300 includes a seal support 312 adapted tospan the feed area channels 308 formed in the terminal side 306 of theplate 302. The seal support 312 circumscribes the header opening 310 andincludes one edge 314 extending laterally past the feed area channels308 toward the header opening 310. A spacer 316 is disposed between theterminal side 306 of the plate 302 and the seal support 312 adjacent theone edge 314. The spacer 316 circumscribes the aperture 310 and formssubstantially fluid tight seals between itself and both the terminalside 306 of the plate 302 and the seal support 312 to block the flow ofreactants through the feed area channels 308.

In the embodiment shown, the conductive plate 25′, the seal support 312,the spacer 316, and the terminal side 306 of the plate 302 are joinedtogether by welding. Other means of joining together the components suchas an adhesive can be employed as desired. Alternatively, a seal (notshown) such as an elastomeric seal can be provided between therespective surfaces of the spacer 316 and the terminal side 306 of theplate 302 and the seal support 312. The clamping force provided by theclamping plates compresses the components to form substantially fluidtight seals therebetween. Additionally, the seal support 312 and thespacer 316 can be integrally formed as a single component or integrallyformed with either the second side 306 of the plate 302 or theconductive plate 25.

Alternatively, for the end plate 24 at the terminal end or dry end ofthe fuel cell stack 10, the flow of reactants to the terminal side 306of the plate 302 can be blocked by bonding a covering (not shown) overthe aperture 310 causing the reactants to be blocked from the terminalside 306 of the plate 302. Alternatively, the terminal side 306 may beformed by refraining from forming the header opening 310 therein.Additionally, the conductive plate 25′ can be formed without havingapertures formed therein.

The electrically conductive adapter plates 25, 25′ transmit thecompressive force from the clamping plates to the end plate assemblies22, 24, sealing members 100 and the seal assemblies 200, 300.Additionally, the conductive adapter plates 25, 25′ provide electricalconductivity between the end plate assemblies 22, 24 and the adjacentclamping plate.

A substantially fluid tight seal may also be formed at selectedlocations between the UEA 16, 18 and adjacent plates 20, 22, 24. Asubstantially fluid tight seal formed between the plates 20, 22 at theaperture 42 is illustrated in FIG. 6. The sealing member 100 is formedin plate 26 of the bipolar plates 20, 22 to circumscribe the aperture 42while the surface 400 circumscribing the aperture 42 in the adjacentplate 26′ of the bipolar plates 20, 22 is substantially planar. Anaperture 402 formed in the UEA 16 is adapted to be in substantialalignment with header opening 42 in the bipolar plates 20, 22 to formthe coolant header. An elastomeric seal 404, 404′ is disposed on anupper surface 406 and a lower surface 406′, respectively, of the UEA 16adjacent to and circumscribing the aperture 402. The seal 404 is incontact with the planar surface 400 adjacent aperture 42 in bipolarplate 22 while the seal 404′ is in contact with the sealing member 100circumscribing the aperture 42 in bipolar plate 20. The clamping forceprovided by the end clamps. (not shown) form a substantially fluid tightseal between the seals 402, 402′ and the planar surface 400 and sealingmember 100, respectively, to prevent coolant from flowing between theplates 20, 22. Flow channels 410 can be formed between the facing plates26, 26′ of each of the plate assemblies 20, 22, 24 to provide fluidcommunication between the coolant header and the coolant chamber 34.Alternatively, apertures (not shown) can be formed in the plates 26, 26′adjacent the seal member 100 or the planar surface 400 between theheader opening 42 and the seals 404, 404′, respectively, to providefluid communication between the coolant header and the coolant chamber34.

The planar surface 400 compensates for a misalignment between adjacentplates 20, 22 which would result in a reduction in the effectiveness ofthe seal between the adjacent plates 20, 22. The adjacent plates 20, 22can have some degree of a lateral misalignment due to a manufacturingvariation, for example. In the embodiment illustrated in FIG. 6, theseal member 100 as illustrated in FIG. 3 a is shown. It should beunderstood that the seal member 100′, 100″, 100′″ as illustrated inFIGS. 3 b to 3 d can be employed to form the seal shown in FIG. 6.

The fuel cell stack 10 featuring the sealing members 100, 100′, 100″,100′″ and the seal assemblies 200 and 300 of the present invention canbe manufactured at a reduced cost compared to a gasket or fuel cellplate employing a typical prior art seal. The sealing member 100, forexample, does not require additional surface finish treatment such asapplying a sealing material thereto. Additionally, the sealing member100 and the seal assemblies 200 and 300 are effective to form andmaintain a substantially fluid tight seal over a wider range ofdimensional variation within the fuel cell stack 10. The effectivenessof the sealing member 100 and the seal assemblies 200 and 300 toaccommodate such variation minimizes the number of critical tolerancesthat must be maintained in the various components of the fuel cell stack10. The minimized number of critical tolerances minimizes amanufacturing cost of the fuel cell plate 26.

From the foregoing description, one ordinarily skilled in the art caneasily ascertain the essential characteristics of this invention and,without departing from the spirit and scope thereof, can make variouschanges and modifications to the invention to adapt it to various usagesand conditions.

What is claimed is:
 1. A seal assembly for a fuel cell comprising: abipolar plate including a first plate, a second plate, and at least oneheader opening formed therein, the first plate including an elongatesealing member formed therein with a first lateral side and a spacedapart second lateral side and at least one sealing surface disposedtherebetween; the second plate including a substantially planar surface;and at least one sealing component adapted to cooperate with the sealingmember to form a substantially fluid tight seal therebetween.
 2. Theseal assembly according to claim 1, wherein the sealing member, theplanar surface, and the sealing component are adjacent to andcircumscribe the at least one header opening of the bipolar plate. 3.The seal assembly according to claim 1, wherein the sealing componentincludes: a unitized electrode assembly having a first surface and asecond surface; a first seal disposed on the first surface of theunitized electrode assembly adapted to form a substantially fluid tightseal between the unitized electrode assembly and the planar surface ofthe second plate; a second seal disposed on the second surface of theunitized electrode assembly adapted to form a substantially fluid tightseal between the unitized electrode assembly and the sealing member ofthe first plate.
 1. The seal assembly according to claim 1, wherein aspace between the first plate and the second plate of the bipolar platedefines a coolant chamber.
 2. The seal assembly according to claim 4,wherein at least one flow channel is formed between the first plate andthe second plate of the bipolar plate, the at least one flow channelproviding fluid communication between the coolant chamber and the atleast one header opening.
 3. The seal assembly according to claim 4,wherein the first plate further includes at least one aperture formedtherein adjacent the sealing member, the at least one aperture providingfluid communication between the coolant chamber and the at least oneheader opening.
 4. The seal assembly according to claim 4, wherein thesecond plate further includes at least one aperture formed thereinadjacent the planar surface, the at least one aperture providing fluidcommunication between the coolant chamber and the at least one headeropening.
 5. The seal assembly according to claim 3, wherein the sealingelement further includes a plurality of apexes and at least one troughformed therebetween, the apexes cooperating to form the sealing surface.6. The seal assembly according to claim 8, wherein the first platefurther includes a first surface and a second surface, the first surfaceadjacent the second seal of the sealing component.
 7. The seal assemblyaccording to claim 9, wherein the trough is elevated in respect to thesecond surface of the first plate.
 8. The seal assembly according toclaim 9, wherein the trough is substantially coplanar in respect to thesecond surface of the first plate.
 9. The seal assembly according toclaim 3, wherein each of the first lateral side and the second lateralside of the sealing member includes an arcuate upper end, asubstantially planar sealing surface disposed in between the firstlateral side and the second lateral side, the planar sealing surfacebeing recessed in respect to the arcuate upper ends of the first lateralside and the second lateral side.
 10. The seal assembly according toclaim 12, wherein at least a first radius and a second radius define thefirst lateral side, and at least a first radius and a second radiusdefine the second lateral side to provide a resiliency to the sealingmember.
 11. The seal assembly according to claim 3, wherein the sealingmember includes a plurality of coextensive elongate protuberances, eachprotuberance having a first lateral side and a spaced apart secondlateral side, with a sealing surface disposed therebetween.